The calorie in calorie out fallacy

The calorie in calorie out fallacy

The calorie in calorie out fallacy:

Obesity in numbers:

Obesity is one of the biggest issues we are facing, and it is only increasing with numbers above 650 million obese adults(data by the World Health Organization).

The biggest problem is that obessity never comes alone and increases the chance of many conditions such as cardiovascular diseases  and diabetes Type II.

If you thought that those were already a lot of problems, then when I tell you that it also comes with a reduction of lifespan of at least 8 years of life in obese patients. Their lifequality also suffers as they have difficulties with even day to day activities due to the diverse effects that it has on health.

Obessity isn’t over

The biggest problem with this condition is the fact that the number of people it affects is still increasing and it is estimated to keep on growing in the following years specially in countries such as the United States and Mexico the percentage of obese people is expected to surpass the 47% and 39%  respectively.

All this information makes us realize how much of a problem obesity is nowadays and how it will continue to worsen if we don’t act against this condition, and for that we have to start by understanding one of the many reasons that have generated the increase in obesity, which is what we could call the ”Calorie in/Calorie out fallacy”.

Are all the calories really the same?

By ”Calorie in/Calorie out fallacy” we refer to the fact that until recently it was believed that the best approach to reduce our weigh, was reducing the number of calories we eat relative to the number of calories we burn.

And the simplest way to approach it would be to simply restrict the number of calories we consume, by reducing how much food we eat, and/or by increasing the quantity of exercise we do.

Photo by Avi Naim on Unsplash

The idea of this approach isn’t completely wrong and it could work, the problem though is that approaching it without taking into account one important fact. Without it, it could turn it into a most grueling effort that could undermine the motivation of those attempting to lose weight and leave them with no results and a sense of defeat that isn’t completely their fault.

Not all Calories are Created Equal

In order to keep this from happening when approaching weight loss, we have to take into account one simple fact, which is that not all calories are the same.

Photo by Artur Łuczka on Unsplash

A simple example to illustrate this fact is that nobody would expect that drinking alcohol and drinking water would have the same effect in our health.

In the same way, as we would consider it stupid to consider both drinks as the same, it is also the case that considering all kinds of calories as the same isn’t exactly the best idea.

The reason why not all calories can be considered as the same is the fact that our body doesn’t treat all kinds of food in the same way.

Our bodies don’t process in the same way food that is full of processed sugars, as it does those that are high in fibber. The reason being that while in the first case their ingestion causes a spike in the levels of glucose in blood, in the second the presence of fibber makes it so that the quantity of glucose that reaches our bloodstreams is more controlled.

We might think:

‘Why should it matter whether we receive glucose spikes? ”,

”Why should I care, does it really make a difference?”

The fact is that it certainly makes a difference and huge one at that.

The reason for the difference between the two situations is that the response they induce in our hormones is completely different, and this is mostly related to a hormone called insulin.

Insulin is also the link between diabetes type II and obesity.

Obesity and Diabetes: Two Faces of the Same Coin

Explaining the why behind the myth

We already spoke about how the idea of calorie in calorie out is flawed, and now that we know that we will present you with another model that explains reality in a better way.

Why calorie in calorie out doesn’t work

The model is based on the idea that the body decomposes all foods into elements it can extract calories from. This model also expects all elements to be treated in the same way, and to be stored in a single storage from which we  would extract energy as needed.

The problem is that in truth not all calories are the same. As we already know the food we eat is formed by different macronutrients. This macronutrients are carbohydrates, proteins and fats and our body treats each of them in a different way.

In contraposition to this one compartment model, the author of The complete guide to fasting presents a 2 compartment model that better illustrates our reality. This 2 compartment model defines the glycogen stores as the first compartment and the fat stores as the second compartment. In order to explain how this works we will use analogy adapted and modified from the book The complete guide to fasting.

Grocery shopping

How our body actually stores energy

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Let’s say you just came from the supermarket. Once you get home you decide that part of what you just bought will be used for the meal you will eat right now. Of course, the quantity you will use for the meal is only a small part of all you just bought and so you will have to store the rest of the food so that it doesn’t go bad.

Part of the food you will store in the fridge, the fridge is quite accessible and whenever you want to cook a meal in the next days you will most likely get food from here. The food you store in the fridge  has to be eaten soon in order for it not to spoil.

Once the fridge is full you have to decide what to do with the rest of the food. Your choice is to prepare the excess food in a way such that it will be easy to use when you want it and decide to store it in the freezer for long term. In this freezer you will also store all the food that you thought you were going to use for the meal but ended up not using (excess food).

And just to make the analogy more accurate let’s say that you have one of those freezers that occupy most of the fridge (or in the analogy presented by doctor Fung, a freezing chamber).

The food you put in the freezer isn’t that easily accessible since it needs time to unfreeze so that you can prepare it, and you will most likely give priority to the contents of the fridge because they will start getting spoilt faster.

The Two Compartment model

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In this analogy the food you use to prepare the meal when you get home are the carbohydrates you obtain from a meal. The fridge could be thought of as your glycogen storage since it is what keeps us going the first days after you start fasting.

The freezer is your fatty tissue and exemplifies how we don’t access this fat until we have almost depleted the glycogen stores and how the fat requires processing in order to be used by the body as energy. To finish, the excess food is an analogy to the excess glucose and proteins you turn into fats.

This analogy helps us differentiate between those elements we obtain from a meal that are used in the moment such as glucose and excess proteins that are converted into glucose. And those elements that we store such as fats and excess glucose that gets turned into glycogen in the liver and  fat.

This analogy is also useful since it shows how our body won’t use fats as its main source of energy unless it has almost depleted its glycogen stores.

Obesity and Diabetes: Two Faces of the Same Coin

What is diabetes?

Diabetes is defined as a ”metabolic disease characterized by chronic hyperglycemia, resulting from defects in insulin secretion, insulin action or both”1,2 .

This means that diabetes is a disease that is characterized by the increase in the levels of glucose in blood above normal levels and by the impossibility or difficulty for the body to deal with  these changes. This problem can happen mainly due to a lack in the secretion of a hormone called insulin, or due to problems in the action of this hormone.

In order to understand why this can cause a disease we have to start by knowing why high  levels of glucose in blood can be a problem.

Effects of Hyperglycemia

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Glucose is a molecule of great importance for the body since this ”sugar” is one of the main sources of energy for us and it especially so, since about 30% of the energy we obtain is used by the brain in the form of glucose, fact that illustrates the need for this compound.

Although the importance of glucose is apparent from what we have just mentioned, this doesn’t mean that having as much as possible of this molecule would be beneficial.

It has been shown that in critically ill patients hyperglycemia can induce organ damage in a wide range of organs among them the liver, pancreas and the brain.

This happens due to mechanisms such as an increase mythoncondrial death and not only does an increase in glucose affect in a negative way, it has also been shown that wide fluctuations of the concentration of this compound can also be negative, since it also increases the production of free radicals3.

How does insulin affect what we just described?

Diabetes and insulin

Insulin is a hormone secreted by a special type of cells named β-cells that are found in the pancreas and it is the hormone in charge of controlling the levels of glucose in blood(also known as glycemia)  by inducing the uptake of glucose by different kinds of cells and also participates in the regulation of carbohydrate, lipid and protein metabolism.

This means that this hormone is the one that is in charge of regulating the levels of glucose and as such is one of the main responsible in limiting any possible damage that excess glucose could cause.

Diabetes happens because there are problems

  1. With the production of this hormone or
  2. With the action of this hormone meaning that it is produced but for some reason it doesn’t work as it should. 4

This problems make it so that the levels of glucose can’t be regulated as they should and so produce spikes of glucose after a meal which in the case of diabetics have to be treated with an injection of insulin to control the levels of glucose.

This is done not only because an excess of this in the blood can cause unwanted effects, but also because the lack problems with the uptake of glucose affect in a negative way the function of cells by limiting the energetic intake of this molecule.


The science of fat (I)

You might be asking yourself ”How are insulin, glucose and fats related?”

Insulin is a hormone mainly known for its role in fat uptake. The levels of this hormone when we aren’t eating are low, and it is only when we eat something that the levels of this hormone increase.

The increase in the levels of insulin isn’t the same for all kinds of food, this is due to the fact that depending on the macronutrient the levels of insulin increase more or less.

The macronutrients that produce the highest increase in the levels of this hormone are carbohydrates, soon we will explain why this would be an expected outcome, followed by proteins and fats being last. Now that we know that insulin is important lets see how it affects fats.

Insulin and its role in fat metabolism.

The usage of fats as a source of energy also depends on the levels of insulin. The reason for this comes from the fact that insulin is one of the main actors in the intake of glucose and its transformation into fats. Meaning that insulin has a role in producing more fats and as such could logically be expected to reduce fat’s usage.

For example, if in the same exact situation the levels of insulin in one person are lower, then that person would have more ease using the fats stored as a source of energy than if they had higher levels of this hormone.

The meaning behind the role of insulin in burning fat can be intuitively understood from the fact that if you just ate a meal it wouldn’t make much sense to burn the energy you have stored as fats instead of using the energy from the food you just consumed.

If instead, you burned the energy from the fats the only thing you would get would be more fat obtained instead from the food you just ate. This is due to the fact that excess energy that isn’t used as heat or stored as glycogen has to be stored as fats, which would make the use of the fats we have stored instead of the food we just ate a little bit of a nonsensical act.


The gatekeeper to the fat treasury

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And not only does it have a role in preventing the usage of fats, by inhibiting lypolisis (aka fat burning), but it also favours the usage of carbohydrates as a source of energy. The implications of this will be further explored in articles about the modern diet and its disadvantages.

The body is constantly using different sources of energy in order to keep itself active and we have to understand that the only thing that changes is the percentage of energy derived from each source.

The role of insulin in this case is to ensure that so long as we have, glucose obtained from a meal or enough glycogen, we use these as the principal source of energy. And it is only once their levels are below a certain threshold that we start to use more fats for energy.

In this sense we could think of insulin as a sort of gatekeeper with many individuals doing rotation to fill the position in a way such that whenever one gets tired the next one in line has already arrived and is ready to assume the role and control the access to the fat stored.

These gatekeepers are pretty good at their job and so long as we have enough glucose the treasury will always be guarded by at least one person. But once we start fasting the gatekeepers start taking longer to fill in the gaps during rotations, until we are completely free to access the fat stores.

Diabetes type I could be thought of as a situation in which the gatekeepers are completely unable to cope up with the job and so we have a lot of time in which there is no one to protect the door.

This means we are unable to keep watch of the treasury and most of our treasure gets stolen and lost.  A way to stop this from happening is to contract mercenaries to stand guard to protect our treasury and keep thieves out of it so that we can keep building up treasure.

In diabetes type I there is a problem in the cells that produce insulin or in the insulin produced in a way such that the person is unable to store glucose as fats and the way to surmount this problem is to inject insulin that works so that we can start using glucose as a source of energy and store the excess glucose as fats.

But how is obesity related to insulin and diabetes type II?

Caloric restriction diets and the road to insulin resistance

How high insulin + Reduced calories = Slowing the metabolism

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Taking into account the 2 compartment model (remember the grocery shopping metaphor) to burn fat you would have to 1) deplete enough of the glycogen stores and 2) reduce the levels of insulin.

When we start depleting our glycogen stores our body starts sending hunger signals. These hunger signals induce the desire to eat more (one of the reasons we feel hungry is that we start depleting our glycogen stores).

When we feel hungry we eat and this induces a spike in insulin, but it also derives part of the glucose we consume into the liver to be stored as glycogen.

If we eat enough to stop feeling hungry, but not to fill the glycogen stores, will keep insulin levels high since we haven’t gotten to the threshold necessary to reduce it.

When we find ourselves in this situation our body decides to decrease our BMR(basal metabolic rate) by burning less energy, this is part of the reason why the low calorie diets make us feel groggy. Since we still have high insulin levels we are unable to burn fat and as such unable to lose weight.

As this cycle repeats, not using all our glycogen and keeping insulin levels high, we can end up developing insulin resistance. The biggest problem with this cycle is the fact that so long as insulin levels remain high we will have a hard time accessing our fat stores.

High insulin = Harder time accessing energy from fats

And this in turn means that the body is forced to slow its metabolism. Which comes with the feeling of groggines. The problems of high insulin levels aren’t limited to only this, but could also end up leading to insulin resistance and this with time to the diabetes type II.

Insulin resistance

Insulin resistance can be understood as the situation in which your cells aren’t able to respond to the insulin levels in your body and as such are incapable of incorporating glucose, which would mean that they can’t use the glucose obtained from a meal as a source of energy, nor use it to produce fatty tissue.

One of the reactions of our body to this kind of situation is the increase of insulin levels in an attempt to force the absorption of glucose into cells and as such to provide them with energy.

The problem with this approach comes from the fact that it is a vicious cycle in which the levels of insulin will keep increasing until your body is incapable of producing levels of insulin high enough or until the levels of insulin are so high that you reduce the fat burning to a minimum and increase the fat storing process to a maximum.

The insulin loop

            Image by Thetowerofscience

If this cycle keep suffering a positive feedback and increasing the insulin levels due to a continuation of the ”normal” diet we could end up increasing the numbers of one of the 21st century’s biggest epidemics, diabetes type II.

Diabetes type II is characterized by abnormally high levels of insulin. This in turn makes it so that the person has a hard time using the fats stored, as well as having  an increase in the quantity of glucose that is stored as fats. In the long term this is associated with a wide variety of diseases mostly cardiovascular as well as an all around increase in mortality rate.

These facts make the vicious cycle that could come from not reducing insulin levels into an incredibly serious threat for our modern day sedentary lifestyle, and make it into a necessity to break this cycle.

Breaking the cycle

Fasting is one of the ways in which we can break this cycle since fasting implies not ingesting food for certain amounts of time which in turn implies that we don’t suffer the insulin spikes that come together with any kind of food.

Another less drastic way of approaching the same problem is to try low carb high fat and protein diets, since the effect on insulin is way higher in carb rich foods, and by reducing their content we can reduce the increase of insulin that comes after a meal.

This approach can be easier to follow since it doesn’t imply restricting food intake and could potentially make fasting easier.

Fasting vs low-carb diets

Understanding the difference

Fasting can be understood as the voluntary stop of any kind of food consumption for a certain period of time. Low carb diets can be understood as the consumption mostly of foods that contain low percentage of carbohydrates and that present mostly fats and/or proteins.

Both approaches have been getting attention in the last decades as ways of counteracting the growing obesity and diabetes problems. The reason for this being that both approaches reduce partially (in the case of low carb) or completely (in the case of fasting) the ingestion of foods composed mostly of carbohydrates in an attempt to break the insulin increase cycle.

In this article we will compare both in terms of how they affect insulin levels (we won’t touch other levels).

And how if your objective is to lose weight fasting could be a better option, and how these two options relate to insulin levels. To understand why insulin levels are important we have to understand what is insulin and its role on our metabolism.

The Pyramid’s Lie: Another way of look at the two compartment model


Once that we know why insulin is important we can understand the difference between these 2 approaches.

To start we have to understand one simple fact, and that is that ” levels of insulin always spike after a meal”. The reason for this is the interaction between our body and the different macronutrients in our food.

The different macronutrients in a meal are carbohydrates, proteins and fats, and the response of insulin to each of them is different.

In order of how strong is the increase of insulin levels for each of them we can see that carbohydrates are the ones that induce the highest increase in insulin levels, followed by proteins and fats.

What this means is that eating the food that usually forms part of the ”normal” diet will produce a high increase in insulin levels, due to the fact that many of us have been taught that the correct diet is one where we eat carbohydrate reach foods such as bread.

And this in turn will reduce the quantity of fat burned since insulin induces fat storage and it would be counterproductive to burn what you are trying to store, we could think of insulin as an artisan and of fats as their work, no artisan would burn the work they poured their energy into, unless they had no other choice.

How do they affect insulin

If we take into account what we just explained  you may think, ”Hey why don’t we just go with a low carb diet?”.

You could be right if your objective mainly to reduce weight this could be a pretty reasonable approach since you would cut on the macronutrient that produces the highest effect in insulin levels, but the problem is that it isn’t the only one.

Metaphor of how low carb still produces a slight spike in insulin
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As we explained before proteins also induce a spike in insulin levels, albeit a smaller increase that carbohydrate rich foods, and this would mean that if your insulin resistance is high it may not be enough to reduce the levels of insulin and lose weight. Although low carb diets are a pretty good option to maintain your current weight in a pretty healthy way.

Now that we know how insulin responds to different macronutrient levels we can understand why fasting and low carb diets are different.

The answer is that since you don’t ingest any kind of food while fasting, your insulin levels will be bound to drop with time since your only energy source are the fats you have stored and only by decreasing the insulin levels can you fully access this energy.

Meaning that fasting could be a pretty interesting way to reduce the insulin levels and fat stored, and this second fact could help you lose weight.

Metaphor of how fasting doesn’t produce spikes in insulin
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Fasting, the fat burning saga

Part one: Ketosis

As we have seen in previous articles, fasting long enough gives us the chance to switch from using glucose and glycogen as main source of energy to using fats as the main source of energy. But what does it really mean to burn fats?


What are they?

To start we have to understand what fats are made of (this explanation will go a little bit into detail but bear with me for a little) .

The fat in our bodies is stored mainly in the form of triglycerides. Triglycerides are molecules made up from 3 fatty acids, and a molecule of glycerol that acts as a backbone for them. The process of burning fats implies breaking up this triglycerides in a way such that, the fatty acids, can go to different kinds of cells and be used directly, while the glycerol, can be turned into glucose by gluconeogenesis in order to supply energy to those cells that can’t use fats.

Now you may be asking yourself ” Sure, now I know what are the fats, but how are ketones related?”

The thing is that there is a small  problem, which is, that not all the cells in our body can obtain energy using fatty acids. The brain for example is in constant need of  glucose being the major consumer of this energy source. In normal situations this wouldn’t be a problem due to the high supply of glucose, but during a fast the supply of glucose is limited.

This means that we have to find another way to supply the brain with energy in a way such that, part of the glucose produced from glycerol, can reach those cells that can’t use fatty acids. And here is where ketones come into play.

Don’t be a picky eater

Why ketones are important

You may be curious about my choice of titles, and I will explain why I chose it, it wasn’t random mind you, but before that lets understand what are ketones.

When we speak of ketones we are referring mainly to 3 different compounds, which are acetoacetate (AcAc), 3-hydroxibutyrate (3HB) and acetone.

The importance of these ketones for us comes from the fact that they can be used as a source of energy for our brain and as such can leave glucose for those tissues that can’t use fatty acids. The advantage in the use of ketones comes from the fact that these molecules are obtained from fatty acids. The importance of ketones and the fact that the brain can use them will be made apparent with the analogy.

ketones are obtained from fatty acids

Tactician’s choices

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Now you may ask, ”Why should I care if ketones come from fatty acids or from any other thigh?”. To exemplify their importance lets use an analogy.

Let’s say you are a tactician in charge of an army in olden times, and your army is currently facing in a battle of attrition that has been going on for a few days. Due to the long battle your army is running low on supplies.

Your army is formed by an incredibly strong cavalry and a few units of infantry and the food has to be divided among them. Although you feel torn about it you give more preference to the cavalry since you know that they are your main card for victory, but you can’t stop giving supplies to your infantry since they form the bulk of your army and your cavalry would be overrun the moment you lose them.

Photo by Patrick Schneider on Unsplash

In this situation when your back is against the ropes and you don’t know what to do, you see a miracle happening, a unit with an ally flag is coming your way and the have supplies!! You feel saved and distribute the new supplies to feed the cavalry while using the ones you already had to feed the infantry. And this is how ketones are important when fating.

When fasting as we said there comes a moment when we are using our fat stores and from this part goes to those organs that can use fatty acids while the glycerol is turned into glucose for the brain and other organs that can’t use fatty acids.

The supplies in this analogy are the glycerol stores, and the cavalry is the brain while the infantry are the rest of the organs that have to use glucose. While the new supplies are the ketones that help save the day, due to the fact that ketones come from transforming fatty acids and as such help feed the brain while giving more room for the usage of glucose for the rest of the organs.

Remember that there are tissues that cant use fatty acids and see themselves forced to fight with the brain for a limited supply of glucose, and you really don’t want to fight with the brain for resources.

In this situation where this tissues see themselves at risk of having less energy that required, is where the ketones are important, since the fact that they come from fatty acids and can feed the brain, they can ease the strain the brain has in the glucose supply.

To summarize, you can think of ketones as an alternative source of supply that gives the foot soldiers a food when it would otherwise go mostly to the brain.

But how does fasting really affect your health?

Fasting and its effect on brain activity

To start, let us think of the last time you had a huge meal. How did you feel after it?.

I am sure the feeling wasn’t one of complete mental wakefulness, and much less a sharpening of your senses.  This situations are usually followed by grogginess and lack of will to do any kind of activity.

This is because once you are satiated your body turns its focus from all other activities, towards just processing the food you ate.

This implies a few changes at the physiological level, among them an increase of blood flow and as such, of oxygen supply, to the organs in charge of processing the food. Which in turn implies a reduction in the supply of oxygen which means, usually a reduction of activity of organs such as the brain.

As well as changes at the metabolic level, since as we have seen all meals imply an increase in insulin levels and such increases are known to reduce the activity of other hormones such as the human growth hormone, known for its impact in mental sharpness.

As we saw in the ancestor’s metaphor, fasting induces a more alert state. This is due to the fact that if your body ”knows” it is in a state of caloric restriction, it tries to sharpen your sense. This strategy our body follows is its way to keep you from missing any possible chance of acquiring food.

And many studies have shown that none of the usual parameters studied to monitor mental acuity show impairment in a fasting state. Neither, the sustained attention, nor intentional focus, nor immediate memory showed a decline.1 2

Fasting has also been shown to improve motor coordination, learning and memory in rats undergoing intermittent fasting. And not only that, but they also showed an increase in the release of the brain-derived neurotrophic factro(BDNF) hormone known to induce the growth of neurons and for its importance in long term mermory.3

This is an incredibly interesting discovery, as this hormone was known to be produced mostly when doing exercise, and the fact that it isn’t limited to exercise but can also be induced by fasting could give us the opportunity to use both to maybe multiply the effects we could get.

Fasting and age

The Role Of

Programmed Cell Death

The relationship between aging and fasting doesn’t limit itself to this, but also affects the so called senescence process. Senescence, also known as programmed cell death, is the process by which a cell is ”destroyed” after a certain amount of time has passed.

This process is useful due to the fact that as a cell keeps on dividing and giving rise to new cells these cells keep on accumulating DNA damage

The accumulation of this DNA damage keeps building up until a point in which the cells lose the proper functionality and can end up multiplying without control which  could  induce diseases such as cancer. You could think of it as a building up a possible cancer cell storage.

By having a PRD (programmed cell death), we can reduce the possibility of this happening, as after a certain amount of time the cells would ”die” and as such we could prevent any possible problems associated with this.

The problem is that this mechanism isn’t 100% fool proof, since many different factors such as diet and environment can give signals that mess up the cell and keep it from going into this programmed death.

Some of the factors that can inhibit PRD, are increased levels of glucose and insulin. This effect is due to the mTOR pathway, a metabolic pathway that is related to nutrient availability. The presence of insulin and glucose activate this pathway and this in turn inhibits different processes that could induce PRD.

This means that most likely, whenever we eat we are inhibiting this process, and while this isn’t a problem in the short term, the accumulation of cells that present defects could induce cancer or other age related diseases.

And, on the other hand, if we fast, and as such keep lower levels of glucose and as such of insulin. We can induce the activity of the mTOR pathway and induce programmed cell death. This triggers an elimination of old cells ( the body usually marks those cells in certain ways) and as such a reduction on that possible cancer cell store.

This is especially true because the use of fats as a source of energy doesn’t activate the mTOR pathway and as such fasting would keep us active, with sharper senses, while at the same time helping us reduce the ”possible cancer cell store”.

To finish let’s see some of the most typical misconceptions regarding fasting.

Fasting misconceptions I

I)Fasting makes you feel sluggish

One of the most common misconceptions we can find about fasting is that fasting makes you feel less energetic and active, and that as such it would be a bad idea if you want to do any kind of productive work.

Let’s explain how your body actually works when you start fasting.

To start we will address the assumption that fasting makes you feel groggy, this notion could come from the fact when you start a diet with a caloric restriction (less energy if you keep on consuming the same kind of foods but in less quantities) you start to feel less energetic. While this is true for caloric restriction diets, it doesn’t apply to fasting, and to understand why it applies in one situation but not the other we need to understand what is the basal metabolic rate.


Another take on why caloric restriction diets don’t usually  work

Photo by Renee Fisher on Unsplash

The basal metabolic rate or BMR is defined as the energy you have to expend in the different processes that are needed to keep you alive and functional, such as breathing, the beating of the heart and other such physiological phenomena, at rest.

The interesting part about the BMR is that it isn’t a constant measure, but rather something that can fluctuate depending on the number of calories ingested and not only can it fluctuate, depending on whether you overeat or restrict your diet go up to 40% more to up to 40% less respectively.

Now that we know what the BMR is and that it can fluctuate, you may be asking ”Why should I care about this thing and whether it changes?”, and the answer is that this decrease in the BMR when you start a caloric restriction is the one responsible for the lack of energy.

Evolution has made it such that we have become adapted to reduce our BMR whenever we detect a lack of calories as a way of conserving energy, since believe it or not the processes that are taken into account in the BMR are the ones that use most of the energy we obtain and so in a situation of caloric restriction it sounds reasonable to reduce the energy expenditure in this processes, and this is also the reason why caloric restriction diets don’t work as well as you would expect.

The body adapts to the reduction of energy intake by reducing expenditure and with it you lose the effects you would expect and once you return to your usual diet it could also mean an increase in weight until your BMR goes up, but the problem isn’t only that, but also the fact that this reduction in BMR is followed by feelings of grogginess and lack of energy.

We aren’t cars

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So now we know what BMR is and one of the reasons of why caloric restriction diets don’t work, but surely you must be thinking, ”But hey I came here to know about fasting and why it wont make me feel like I have just been hit by a truck and if caloric restriction makes me feel like shit then surely so does fasting”.

And I will answer that but before we get to it we have to start by tearing up a statement which is : ”We need to eat in order to feel energetic”.

This notion comes from the fact that if our body works by burning the energy found in the food we eat, then if we don’t eat we could think that we would end up like a car running on fumes and that only by ingesting more food could we fill the tank fuel to keep going.

Although this sounds logical, the thing is that we aren’t cars and in this case the difference between us and cars that we have to focus on is the fact that a car only has whatever you put in the fuel tank to keep it going, but that isn’t our case.

Since we have something that stores all the excess energy we obtain in meals and that we can use as an energy source, and those are the fats.The fact that we have fats means that even if we don’t eat anything we can have a steady access to energy to keep us going

Answering the question

Why fasting doesn’t make you go into ”starvation mode”?

1) Ancestors and choices

Photo by Mario Álvarez on Unsplash

Okay okay, now you are surely thinking “Sure we aren’t like a car and we have fat but that still doesn’t answer why we won’t feel tired while  we fast” and now we will see different answers for this, starting with a more intuitive one and then going to a more in depth one.

To explain the intuitive answer lets use an example, lets say you are one of our ancestors and that you live mostly as a hunter/gatherer. It has been a while since you last ate anything and you start feeling quite hungry, in this scenario your body could take 2 different paths, lets call them A and B.

In the case of path A your body decreases the rate of its metabolism, this could seem like a great idea and depending on the situation since it would mean that by decreasing your BMR(here is why we explained this at first), you would expend less energy and that also means that you would save up more energy, this in the case of caloric restriction would be a pretty good idea since you would be sure to get some calories even if they were less than before.

The problem is that this decrease in BMR also means a decrease in your energy levels and alertness meaning that you would be less vigilant and this in turn means that you could end up missing chances to hunt or to gather because of a lack of cognitive agility.

And this could in the long run make you die a slow death due to the fact that although you spend less energy with a lower BMR you are still spending it and so you have a time limit. In one of the worst cases you could mistake a poisonous plant for an edible one due to lack of a sharp mind.

Now , in the case of following path B, which is the one that actually happens, instead of slowing your metabolism you ”rev it up” to stay sharp and alert and while it could be seen as a bad idea at first as you would spend more energy, in truth this course of action is better when you don’t really know when you will have your next chance to it so that you can capitalize on any opportunity you find.

2) Why I explained BMR

With the intuitive answer out of the way let’s get into a more detailed one, let’s get into some of the reasons why it happens the way it does.

Once you start fasting that means that your caloric intake goes to 0 meaning that you obtain 0 energy and as we saw the BMR usually follows the trends of your energy intake, but of course, it can’t go to 0 since that would mean giving up on all the different processes that keep you alive and as such you would die.

So that means that your BMR always has to be above a threshold to keep you going and the way it does this is by switching from a metabolism based on glucose of which we have a very limited store to the fats.

While you could think of glucose as the same as the fuel a car uses, and as such as something that has to be supplemented every so often, the fats are what make us different from the cars since they give us a chance to sustain ourselves on the long run without constant ingestion of food.

Once your body has  been fasting long enough something like a switch goes on and  it stops using carbohydrates as a source of energy(mainly glucose) and starts using the fats stored in your body.

And it is through the use of this fats that it can keep the BMR and not only that but also accelerate the metabolism, since once you switch to using mainly fats you discover that you have a wealth of resources to use energy and this gives you the opportunity to stay sharp even after not eating for a long time and as such to make the most of all the chances to obtain aliments.

One of the ways in which your body makes this switch and keeps itself going strong is by the secretion of the human growth hormone(HGH). In a longer article explain how this works thanks to gluconeogenesis and how the fats aren’t exactly what we use for energy.

II)Fasting makes you lose muscle

Since this is one of the most frequent doubts about fasting , and I am sure you came here for this, lets start with the answer:

Fasting doesn’t burn muscle


What is gluconeogenesis

Gluconeogenesis is the process by which using as a base molecules such as pyruvate, which are obtained from compounds different from carbohydrates. By using these molecules gluconeogenesis gives us carbohydrates such as glucose.

The word etymology of the word describes the process perfectly, since gluco– is a derivative of the word glyco which comes from the greek glykys, word that means sweet, and the word neo- and genesis- which mean respectively new and creation. So when you put them together you get the meaning of the process

Gluconeogenesis = Generation of new ”sweets”

In this case we refer to them as sweets because two of the most well known carbohydrates are glucose and sucrose, both of which are known for having a sweet taste and sucrose is what we use whenever we put sugar in our drinks.

From this we can summarize that gluconeogenesis is the process by which using molecules which many times come from a source different from carbohydrates, you can produce carbohydrates.

When is gluconeogenesis important?

You might think, why is this process important when we could just eat the carbohydrates ?

The fact is that as we saw if you want to go into fasting or use a keto diet you will still ”need” a suply of glucose, and this is due to the fact that our body has grown used to this compound as a source of energy mostly for organs such as the brain, and as we saw, there are a few organs that are unable to use other sources of energy.

Meaning that when you can’t get glucose from outside sources, your only option would be to actually create it yourself, and here is where gluconeogenesis comes into play.

By using this process you can supply your organs with glucose even when you aren’t getting any from outside sources and as such you can continue with you normal metabolism even while in ketosis.

So now that we know why gluconeogenesis is important the next step is to understand how the process works. But before that let’s see which are the main molecules we use for the process.

Which are the sources of energy?

For this process we can use different molecules as a base, among them:

  • Aminoacids which as we all know come from decomposing the proteins we get through our diet
  • Lactate which is what gives us when it accumulates after intense exercise
  • Glycerol Which we saw was produced during ketosis as we decomposed the lipids from our diet.

Those three are the main sources of molecules that we use as a base for gluconeogenesis, meaning that since during ketosis we obtain glycerol, we can use it as a source of the basic compounds to obtain glucose.

Why would we believe that fasting burns muscle?

The importance of this process comes from the fact that glucose is one of the main molecules used for energy, specially taking into account the modern high carb diet.

The importance of this concept for us is due to the fact that in the initial stages of fasting, specifically between the 2 and 4 days timeframe since the start of the fast, you see a rise in the use of aminoacids for the obtention of glucose.

This is because high carb diets make it so that our body is used to consuming glucose as its main source of energy and this induces the use of other molecules to make up for the lack of glucose resulting from fasting, which is specially accentuated by the deplition of the stores of glycogen, the way in which we store glucose, in our livers and as such a drop in the levels of glucose in blood which is what induces gluconeogenesis.

Answering the question

1)Why burning the furniture is a bad idea?

Photo by Olivier Guillard on Unsplash

Now we know where this idea of burning muscle as a fuel comes from, the next step is to understand why it doesn’t make much sense. To begin we have to agree on the fact that muscles are what let you move and go about all the daily activities you have to do, meaning that muscles let you search and obtain the food necessary to keep you alive.

So now that we agree on this fact lets use an example to explain why it would be a pretty bad idea to use muscle as a source of energy. Lets say you are a woodworker and live in a log cabin close to forest and that every week you go to the forest and cut some trees.

Of the trees you cut a part would be used to produce goods you could sell in order to obtain money and live, another part would go to making the furniture for your house and to repair anything borken, and as for the excess you just store to use as firewoood.

Now let’s say one day you are trapped in your house due to a snowstorm and you can’t get out or ask for help and are forced to stay inside. Of course, you already sold all the parts that you could sell for that week and have enough food to keep you going so the only problem is the cold.

Due to the cold, you feel a need to start a fire to warm the house and so you face a choice,

  1. You use the furniture you worked on to start the fire or
  2. You use the firewood you stored.

So if your answer is to use the firewood, then congratulations, you chose the same as our body does when fasting. In the same way as you wouldn’t use the furniture you dedicated your time and effort to produce, the body wouldn’t rely on the muscle or the so called furniture of the body, but would rather use the fat stored inside since the whole point of storing fat is to use it as a source of energy when there is no food intake and you need energy to keep you going, or in this case to keep the cold at bay.

This simple metaphor can illustrate how using muscle as a source wouldn’t be a good idea, specially since the proteins are not only the furniture but also the house.

Now that we have an answer lets reinforce it with another perspective based on a more biological point of view.

Ancestor and choices (II)

Photo by Mario Álvarez on Unsplash

To explain the intuitive answer lets use an example, lets say you are one of our ancestors and that you live mostly as a hunter/gatherer. It has been a few days since you last ate and your glycogen stores are running really low and you have to start using a source of energy apart from glucose.

In this situation you have 2 choices, 1) You proceed to use the proteins in your body or 2) You start using the fats you have stored.

Of course after having seen the first metaphor you choose the second option, but here lets explain another reason as to why the second option would make sense from a more evolutive standpoint.

Choosing to use proteins as a source of energy is something we actually do all the time as we do use fats all the time and glucose all the time.

That is because the body is always using all three kind of molecules in a sort of equilibrium, being the primary source of energy the glucose if you follow a standard diet and being the fats your principal source if you follow a keto diet or when you fast for long enough.

The only situation in which you would use proteins as your primary source of energy would be in the latter stages of starvation. When you have used all the fat stores and have no other way to provide your body with energy and as such you have to destroy proteins that make you up, remember that proteins aren’t only part of muscle but are rather part of all your cells and necessary for the plethora of processes they need to stay alive.

This means that using the proteins in your body would be akin to burning your house to keep you warm, it could work in the very short term, not really but well, but will cause irreparable damage in the long run. It would certainly debilitate our ancestors and make him unable to search for food and hasten his death.

Data and facts

Many studies have shown that prolonged fasting produces no adverse effects on lean body mass, muscle and bone, and that the only parameter that suffers noticeable changes is the body fat percentage.

Fasting has also been shown to not only not affect the quantity  of protein consumed on a non fasting situation, but to even reduce the protein consumption and to induce a ”conservation” of proteins as we can observe in the graph. This facts back the claim that we don’t burn more proteins during a fasting period.

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Consult a doctor before doing anything in this article.The material in this article is for informational purposes only. As each individual situation is unique, you should use proper discretion, in consultation with a health care practitioner, before undertaking the diet in this article.

The author  expressly disclaims responsibility for any adverse effects that may result from the use or application of the information contained in this article.

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